Based on a shounen manga by Adachi Mitsuru, serialised in Weekly Shounen Sunday.

Cross Game is the story of Kou Kitamura and the four Tsukishima sisters, Ichiyo, Wakaba, Aoba, and Momiji. The Tsukushima family runs a batting center with an attached coffee shop, and Kou's father runs a neighboring sporting good store. Wakaba and Kou were born on the same day in the same hospital, and have been close friends since childhood?close enough that Wakaba treats Kou as her boyfriend, even though nothing is officially declared. Aoba, who is one year younger than Wakaba and Kou, doesn't like how Kou is \"taking\" her sister away from her and claims she hates him.